1. Field of the Invention
The present invention relates to the shaping of sheets of deformable materials such as glass. More particularly, the present invention relates to the shaping of glass sheets to a compound bend while in contact with a deformable vacuum mold.
2. Description of Patents of Interest
U.S. Pat. No. 4,277,276 and U.S. Pat. No. 4,297,118, both to John D. Kellar and Gordon F. Pereman, disclose the bending of glass sheets while supported in engagement against a vacuum mold. In these patents, a flat glass sheet is brought into engagement against a lower wall of a vacuum mold that is apertured so that air can be sucked in through the apertures of the lower wall to hold a flat glass sheet in engagement against the lower wall. Means is provided to deform the vacuum mold and shape its lower wall to a shape corresponding to that desired for a bent glass sheet. The glass sheet is softened sufficiently prior to its vacuum engagement against the lower wall of the vacuum mold so that when the mold deforms, the sheet supported thereagainst by vacuum also deforms.
U.S. Pat. Nos. 4,197,108 and 4,272,274 to Frank et al disclose apparatus for bending glass sheets into cylindrical bends wherein glass sheets are conveyed into a shaping station on conveyor rolls and are lifted on a grooved shaping mold having a plurality of spaced elongated shaping members extending completely across a dimension of the shaping apparatus. The shaping members are separated by grooves that extend completely across the dimension of the mold, so that when the grooved shaping mold is lifted from a position beneath the conveyor to a position above the conveyor, the lifted glass sheet immediately above the mold sags by gravity to conform to the shape of the elongated shaping areas between the continuous elongated grooved portions. The glass is lifted into vacuum engagement against a downwardly facing wall of an upper vacuum mold having a downwardly facing wall of desired configuration, the lower lifting mold is lowered to below the level of the conveyor rolls and a ring-like member is transported into the shaping station below the upper vacuum mold and above the conveyor rolls to enable the shaped glass sheet to be transferred by releasing the vacuum that supports the bent glass sheet against the lower wall of the upper vacuum mold. Preferably, the upper vacuum mold is moved vertically to a position near the conveyor rolls initially to minimize the lifting required for the lower mold, and then the vacuum mold is lifted while the lifting mold is lowered after the upper vacuum mold engages the rising glass sheet by vacuum.
In both types of apparatus described previously, the glass has been limited in its shaping to a relatively easy to accomplish shape about one axis of curvature. The need for more complicated shapes made it necessary for the glass sheet bending art to improve on the apparatus existing at the time of the present invention.